What do you mean by presbyopia ? How is it corrected ?

Explanation

1) Presbyopia is a vision defect when the ability of accommodation of the eye usually decreases with ageing.
2) For most people the near point gradually recedes away. They find it difficult to see nearby objects clearly and distinctly.
3) This happens due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens. This effect can be seen in aged people. Sometimes a person may suffer from both myopia and hypermetropia with ageing.
4) To correct this tyoe of defect of vision we need bi-focal lenses which are formed using both concave and convex lenses. Its upper portion consists of the concace lens and lower portion consists of the convex lens.